1. Field of the Invention
This invention relates to a film assemblage including a film cassette, a plurality of film units of the self-developing type, and a dark slide which when removed from the film cassette functions as an imbibition chamber so as to protect a subsequently exposed film unit from further exposure by the ambient light.
2. Description of the Prior Art
The field of instant photography has advanced to the state where an integral self-developing type film unit may now be exposed and passed between a pair of rollers which spread a processing liquid across the photosensitive layer thereof to initiate formation of a visible image in the film unit while simultaneously moving the film unit through a short dark chamber and into the ambient light without adversely fogging or further exposing the film unit. A prime example of such a camera is the SX-70 Land Camera, manufactured by Polaroid Corporation of Cambridge, Massachusetts while a typical film unit may be of the type shown in FIGS. 2-4 of U.S. Pat. No. 3,647,437 granted to Edwin H. Land on Mar. 7, 1972. Basically, this is possible because the film unit is provided with an opacification system which (1) prevents further exposure of the exposed photosensitive layer in those areas which have been covered or treated by the processing liquid containing an opacifier and (2) also cooperates with the dark chamber to prevent actinic ambient light from being "piped", i.e., being transmitted, longitudinally along a transparent outer layer of the film unit until it reaches a position above the photosensitive layer which has not been covered by the processing liquid. However, if the film unit does not have an opacification system or if the exposed photosensitive layer of the film unit is only protected on one side such as by an opaque backing sheet or an opaque layer within the film unit, then provision must be made to maintain the exposed photosensitive layer in a light free environment until the processing liquid has imbibed the film unit to the extent that it is no longer susceptible to being adversely affected by the ambient light. One proposed solution is to provide the camera with an imbibition chamber such as shown in U.S. Pat. Nos. 4,034,386, 4,032,937 and 3,996,595 which fully encloses the exposed film unit or with an imbibition chamber as disclosed in U.S. Pat. No. 4,072,968, which protects the exposed film unit on only one side thereof. While the chambers in the above-noted patents perform their intended functions well, they are not directly related or tied into the type of film unit being exposed. For example, if one were to expose a film unit which did not have an opacification system in the cameras defined in U.S. Pat. Nos. 4,034,386 and 4,034,937 the chambers described therein had better be connected to the cameras or the exposed film unit will be further exposed when it exits from the camera. Also, such a film unit could not be used with the camera described in U.S. Pat. No. 4,072,968 since it only has provision for protecting one side of the emerging exposed film unit. Still further, all of the systems described in the above-noted patents would appear to deprive the photographer from taking a rapid sequence of exposures when using film units having a total opacification system since it appears that each exposed film unit must be removed from its imbibition chamber before another film unit can be exposed. True, a rapid sequence of exposures may be taken with the systems of the U.S. Pat. Nos. 4,034,937 and 4,034,386 patents if the photographer knows ahead of time that the film units contained therein have a total opacification system and therefore removes the chamber from the camera before taking any exposures. But, absent any indicia as to the type of film units contained within the camera, it would appear that one using such a camera for the first time in months may not be absolutely sure what type of film units are contained therein.
From the foregoing it can be seen that if cameras of the type described in the above-noted patents are to be used with film units containing full opacification systems and with those having no opacification system or less than a full opacification system, that it would appear to be more desirable to relate the imbibition chamber more directly to the type of film unit being exposed. This may be done by tying the two to each other when the film assemblage is originally being put together, i.e., make the imbibition chamber and the film units part of the same film assemblage.